Objective To investigate the effect of the film thickness on the growth rate, crystallinity, light transmission and resistivity of ZnO:Si films. Methods Five samples with different thicknesses of ZnO:Si films were obtained on glass substrates by means of direct current magnetron sputtering system with different deposition time. Comparatively studies were carried out on growth orientations, structural characteristics, surface morphologies, electrical parameters and light transmission curves of these films. Results The results showed that all 5 samples were polycrystalline films with preferred orientation of (002) along the c-axis perpendicular to the substrate. When the film thickness increased from 207. 6 nm to 436. 1 nm, the grain size of films increased, the level of crystallinity increased, and the resistivity decreased, however, when the film thickness further increased from 436. 1 nm to 497. 8 nm, the degree of crystallization decreased and the resistivity increased. The average transmittance of all 5 samples was higher than 91. 7% in the visible light range. Conclusion Therefore, the film thickness strongly affected the electrical properties of ZnO:Si thin film, and had less impact on its optical transmittance.